Need help wiring contactor to REC Q BMS w/o pre-charge relay - emitter / collector pins?

Ssybert

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Hi all, I asked this question in another thread as part of a larger issue but think it may be best to be a separate topic as I cannot be the only person with this question.

I have a REC Q BMS which I opted not to buy the pre-charge relay for. There is no documentation on how to wire the contactor to the BMS w/o the pre-charge circuit.

The pins on the BMS which the pre-charge relay would connect to are labelled "emitter" and "collector". I know these are legs of a transistor and doing some research, it sounds like the current flows through the collector, gets amplified and sent out the emitter. In this application, do I just feed the collector with +24v from my battery pack and drive the contactor from the emitter output? Will this just act as an open/closed circuit when the BMS wants to open/close the contactor?

Do I need an additional relay in between the contactor and BMS and NOT drive the contactor directly from the output of the emitter?
I wish there was better documentation on this. I'm leaving for a trip on Thursday and this is one of the last pieces of my puzzle. Any help from anyone familiar with the REC BMS products would be appreciated.

Scott
 

Pyrofx

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The relay pins are just a switch . Positive in , out to relay, out of relay to ground.
 

Pyrofx

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Stand by on that. Let me get to the shop and confirm . But I think that's what they told me and I tested with a VOM
 

brewmatic

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That BMS output can provide a very limited current (usually 20-100 mA) . So to drive a contactor you will need to use a MOSFEET or high amp bipolar transistor. Bit what are you trying to achieve? Pre-charge requires not only a contactor, but some additional circuitry.
 

Pyrofx

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Ok. Measured it. The 3 outputs on the out side of the connector is so you can run either N/O or N/C . It's how my gigavac were wired before I had delays.
 

Ssybert

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I'm sorry guys, let me clarify a bit. I did NOT buy a pre-charge relay. Looking at the install documents, the per-charge relay is activated via pins 1 & 2 on the IO terminal strip. An image in the manual identify pins 1 & 2 as "relay pins". The description further down details these pins as:

1 - MPPT remote ENABLE/charge open collector
2 - MPPT remote ENABLE/charge open emitter

This is where I'm being thrown off. The use of these transistor terms scare me from attempting to send current into either of these pins or put too large of a load on them trying to drive the contactor through them. Are pins 1 & 2 simply an internal relay intended to open and close the contactor either directly or via the pre-charge circuit? Will this relay handle the load of the contactor? Do I just apply +24 to pin 1 and the contactor to pin 2?
 

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DerpsyDoodler

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I'm sorry guys, let me clarify a bit. I did NOT buy a pre-charge relay. Looking at the install documents, the per-charge relay is activated via pins 1 & 2 on the IO terminal strip. An image in the manual identify pins 1 & 2 as "relay pins". The description further down details these pins as:

1 - MPPT remote ENABLE/charge open collector
2 - MPPT remote ENABLE/charge open emitter

This is where I'm being thrown off. The use of these transistor terms scare me from attempting to send current into either of these pins or put too large of a load on them trying to drive the contactor through them. Are pins 1 & 2 simply an internal relay intended to open and close the contactor either directly or via the pre-charge circuit? Will this relay handle the load of the contactor? Do I just apply +24 to pin 1 and the contactor to pin 2?
I don't understand why you're worried about the BMS precharge functionality when you don't have precharge circuitry to apply. I imagine those precharge circuitry connections should be left unconnected? i dont know anything about this BMS and never looked at the manual, so take my 2 cents with a grain of salt. I suggest sitting down and reading through the manual, though. You'll probably end up answering your own questions.
 

Pyrofx

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I don't understand why you're worried about the BMS precharge functionality when you don't have precharge circuitry to apply. I imagine those precharge circuitry connections should be left unconnected? i dont know anything about this BMS and never looked at the manual, so take my 2 cents with a grain of salt. I suggest sitting down and reading through the manual, though. You'll probably end up answering your own questions.
No you will not.
Rec documentation sucks a big .......
This is simply an internal relay . .7 Amos at 60 v
 

Ssybert

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No you will not.
Rec documentation sucks a big .......
This is simply an internal relay . .7 Amos at 60 v
Pyrofx and others, thank you for your support. This was the confirmation I was looking for before I sent +24v into any of these pins. I configured my contactor to be powered from pin 2 while applying my constant +24 to pin 1 and it looks to be working correctly.

For anyone else running in to this issue, ignore the unnecessarily complex and confusing explanation of pins 1 & 2 in the manual and wire it like this:

Pin 1: Direct to + (positive) side of battery pack - in my case, +24
Pin 2: Wire direct to + (positive) lead on contractor actuator.

Contactor actuator - (minus) lead: Wire to negative side of pack AFTER shunt (if you have one) so you can include it in the load measurements.

Thanks again all!
 
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